Eriocalyxin B ameliorated experimental autoimmune prostatitis via modulation of macrophage polarization through gut microbiota-mediated vitamin D3 alteration.

Background: Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is a often heterogeneous condition in urology. Accumulating evidence suggests that the autoimmune response against prostate antigens is related to CP/CPPS. The gut microbiota may be a possible cause of a number of autoimmune diseases. Eriocalyxin B (EriB) is used as an anti-inflammatory treatment for autoimmune disorders. The underlying mechanism of fecal metabolome involved in CP/CPPS treatment by EriB remains unclear.

Methods: The experimental autoimmune prostatitis (EAP) mouse model was generated by subcutaneous immunization. Macrophages, inflammatory cytokines, intestinal microbiota, and fecal metabolome of the mice were analyzed. The alteration of the fecal metabolome was investigated in detail in EriB-treated EAP mice and confirmed by in vitro experiments.

Results: EriB ameliorated significantly decreased prostate inflammation in EAP mice and promoted macrophage phenotype polarizing from M1 to M2. The gut microbiome was altered, and intestinal barrier damage was improved by EriB treatment. Furthermore, the enrichment of vitamin digestion and absorption pathways in the fecal metabolome revealed that vitamin D₃ was altered by EriB. In vitro experiments confirmed that macrophage polarization from M1 to M2 was promoted by vitamin D₃. Finally, fecal transplantation from EriB-treated mice markedly reduced inflammatory indicators and the macrophage M1/M2 ratio in pseudogerm-free EAP mice. In our study, the immune state of macrophage regulated by gut microbiota-mediated vitamin D3 alteration was first time revealed in EAP treatment.

Conclusions: EriB ameliorated in mice with EAP, the gut microbiota mediates vitamin D₃ alterations to modulate macrophage phenotype polarizing from M1 to M2.